Department of Biological Sciences, Auburn University, Auburn, Alabama, USA.
PLoS One. 2013;8(1):e54936. doi: 10.1371/journal.pone.0054936. Epub 2013 Jan 22.
Xylella fastidiosa is a bacterial plant pathogen that infects numerous plant hosts. Disease develops when the bacterium colonizes the xylem vessels and forms a biofilm. Inductively coupled plasma optical emission spectroscopy was used to examine the mineral element content of this pathogen in biofilm and planktonic states. Significant accumulations of copper (30-fold), manganese (6-fold), zinc (5-fold), calcium (2-fold) and potassium (2-fold) in the biofilm compared to planktonic cells were observed. Other mineral elements such as sodium, magnesium and iron did not significantly differ between biofilm and planktonic cells. The distribution of mineral elements in the planktonic cells loosely mirrors the media composition; however the unique mineral element distribution in biofilm suggests specific mechanisms of accumulation from the media. A cell-to-surface attachment assay shows that addition of 50 to 100 µM Cu to standard X. fastidiosa media increases biofilm, while higher concentrations (>200 µM) slow cell growth and prevent biofilm formation. Moreover cell-to-surface attachment was blocked by specific chelation of copper. Growth of X. fastidiosa in microfluidic chambers under flow conditions showed that addition of 50 µM Cu to the media accelerated attachment and aggregation, while 400 µM prevented this process. Supplementation of standard media with Mn showed increased biofilm formation and cell-to-cell attachment. In contrast, while the biofilm accumulated Zn, supplementation to the media with this element caused inhibited growth of planktonic cells and impaired biofilm formation. Collectively these data suggest roles for these minerals in attachment and biofilm formation and therefore the virulence of this pathogen.
速生菌是一种感染多种植物宿主的细菌性植物病原体。当细菌定殖于木质部导管并形成生物膜时，疾病就会发展。本研究采用电感耦合等离子体发射光谱法（inductively coupled plasma optical emission spectroscopy）检测了生物膜和浮游状态下该病原体的矿物元素含量。与浮游细胞相比，生物膜中铜（30 倍）、锰（6 倍）、锌（5 倍）、钙（2 倍）和钾（2 倍）的积累量显著增加。其他矿物元素如钠、镁和铁在生物膜和浮游细胞之间没有显著差异。浮游细胞中矿物元素的分布与培养基成分大致相似；然而，生物膜中独特的矿物元素分布表明了从培养基中积累的特定机制。细胞表面附着试验表明，向标准速生菌培养基中添加 50 至 100µM 的铜可增加生物膜形成，而较高浓度（>200µM）则会减缓细胞生长并阻止生物膜形成。此外，铜的特异性螯合作用可阻断细胞表面附着。在流动条件下的微流控室中培养速生菌的实验表明，向培养基中添加 50µM 的铜可加速附着和聚集，而添加 400µM 的铜则会阻止这一过程。在标准培养基中添加锰可增加生物膜形成和细胞间附着。相比之下，尽管生物膜积累了锌，但向培养基中添加这种元素会抑制浮游细胞的生长并损害生物膜形成。综上所述，这些数据表明这些矿物质在附着和生物膜形成以及该病原体的毒力方面发挥了作用。
